Field of the Invention
The present invention relates primarily to removal of components in electronic systems, and more particularly, to removal of components in high density systems in which individual components are bonded to a substrate with little separation between them, but has much broader application.
In the high density packaging system described and claimed in the above-identified related patents and applications, there is a need to be able to remove an individual component such as an integrated circuit chip from a substrate when that chip is surrounded by other chips which are positioned very close to it. As explained in application Ser. No. 912,456 cited above, these chips can be placed essentially edge-to-edge. For several reasons, the resulting narrow separations between adjacent chips make it impossible to effectively remove the chips by gripping their sides or prying them out with a lever. First, such actions are essentially certain to damage either the chip being removed or adjacent chips and more likely both. Second, a gripping tool or lever which has a thickness which is less than the separation between the chips is too weak or too flexible to be effective. Vacuum chucks and similar apparatus which is intended to lift and place unencumbered chips into packages or other mounting structures are ineffective for removing such chips because the relatively small surface area of such a chip (typically on the order of 1/4 inch by 1/4 inch or having a surface area of 1/16 of a square inch) severely limits the lifting force which can be provided by a vacuum under atmospheric conditions. Further, any technique which drills, breaks or chips the components is unacceptable because the resulting silicon dust, grains and chunks can contaminate other chips and interferes with mounting a replacement chip in place of the removed chip and prevents effective post-removal failure analysis of a removed chip.
Since the type of packaging disclosed in the above-identified related patents and applications is intended for use in high density, expensive systems in which high reliability is important, it is considered highly desirable, if not essential, that a defective chip, or one which has failed during use, can be removed in a manner which enables post-removal failure analysis of the chip to be conducted in a normal fashion. Therefore, the removed chip must not be damaged or destroyed during the removal process.
Consequently, there is a need for a component or chip removal method and apparatus which enables such chips to be removed without adversely affecting adjacent chips and without impairing the ability to conduct failure analysis on the removed chip in the event that the removed chip is a defective or faulty chip.